CVE-2026-18109 W3 Total Cache <= 2.10.3 - Unauthenticated Stored Cross-Site Scripting via Comment Author Name
Unauthenticated attackers can inject arbitrary scripts via comment author names in W3 Total Cache when Lazy Load Images is enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-18109?
CVE-2026-18109 is a high-severity cross-site scripting vulnerability in boldgrid W3 Total Cache, published on 14 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The W3 Total Cache plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Comment Author Name in all versions up to, and including, 2.10.3 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This vulnerability is only exploitable when the Lazy Load Images feature of W3 Total Cache is enabled, as the unsafe re-emission occurs exclusively within the LazyLoad mutator's img tag rewriting step.
Weakness: CWE-79
Which versions are affected by CVE-2026-18109?
How do I fix CVE-2026-18109?
No fix has been published for CVE-2026-18109 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-18109 being exploited?
There is no known exploitation of CVE-2026-18109 in the wild and no public exploit code.
Sources
Also known as GHSA-9qc5-qhm2-7hh3.